Multicolor NTT CCD photometry of the post-core-collapse globular cluster NGC 6397.

Abstract

view Abstract Citations (20) References (35) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Multicolor NTT CCD photometry of the post-core-collapse globular cluster NGC 6397. Alcaino, G. ; Liller, W. ; Alvarado, F. ; Kravtsov, V. ; Ipatov, A. ; Samus, N. ; Smirnov, O. Abstract We have carried out multicolor (UBVI) CCD photometry for more than 2500 stars (12(m<V<22^m) ) in the field of the nearby globular cluster NGC 6397. We find the main-sequence turnoff at VTO=16.45+/-0.05, (B-V)TO=0.550+/-0.012, (V-I)TO=0.790+/-0.010, and (B-I)TO= 1.340+/-0.015. The reddening value is found to be E(B-V)=0.17+/- 0.04. Our comparison of the color-magnitude diagrams with isochrones from \cite{vbb85} and \cite{bvb92} shows that the cluster's age somewhat exceeds 16 Gyr in the scale of Bergbusch & VandenBerg isochrones and 18 Gyr in the scale of VandenBerg & Bell isochrones. The mean main-sequence locus for NGC 6397 in the V-(B-V) and V-(B-I) diagrams is well reproduced by both sets of isochrones in a wide magnitude range. We estimate the upper limit for binaries population in the studied cluster field, at r ~ 8' from the cluster center, as ~ 9%. We have compared the main sequence luminosity functions for NGC 6397 and M 4 (\cite{aea97}). For NGC 6397, we find a luminosity function depression at V=18.0, similar to that noticed for M 4 at V=18.6 but less significant. Publication: The Astronomical Journal Pub Date: September 1997 DOI: 10.1086/118537 Bibcode: 1997AJ....114.1067A Keywords: GLOBULAR CLUSTERS: INDIVIDUAL: NGC 6397 full text sources ADS | data products SIMBAD (14)